[Linux] Add initial perf jitdump support

[sdmaclea]

Linux uses the perf tools to profile application. The linux 4.10 kernel added support for a perf jitdump format.

It has allows better JIT support for perf. Specifically allowing adding:

• native code so perf can show disassembly of JIT functions.
• adding debug info to support source line annotation.
• adding unwind info to better support stack unwind.

I believe this will also allow us to properly support ready to run images.

The app must

• create the jitdump file. Specification
• Inform perf inject of its presence by calling mmap with the filename.
• Add JIT_CODE_LOAD records
• Optionally add JIT_DEBUG_INFO records
• Optionally add JIT_CODE_UNWINDING_INFO records

It is used like this

perf record <app>
perf inject --jit
perf report

/cc @dotnet/dotnet-diag

[sdmaclea]

/cc @janvorli

[adamsitnik]

Is this going to help with https://github.com/dotnet/coreclr/issues/25965 ?

/cc @damageboy

[damageboy]

@adamsitnik I definitely think so!

@sdmaclea I noticed you self-asssigned this.
Does this mean you will be working on this or is this "up for grabs"?

[sdmaclea]

I am debugging a draft patch to implement the JIT_CODE_LOAD records. I plan to create a WIP PR today.

The current patch allows annotating the disassembly of the JITted functions.

I will start looking ar the ReadyToRun functions soon.

I don't plan to add the JIT_DEBUG_INFO or JIT_CODE_UNWINDING_INFO records yet, so that would be "up for grabs".

[damageboy]

@sdmaclea Very cool!

I'd love to test this out if you feel like sharing a branch at some point.

I might also look into the JIT_DEBUG_INFO records, I've peeked around CoreCLR code previously around the internal representation, would be interesting to see if I could pull that off :)

[sdmaclea]

@damageboy Thanks for the offer to help. I uploaded dotnet/coreclr#26897, additional debugging would be helpful.

[damageboy]

@sdmaclea
I'm just finishing a family vacation. Will start testing early next week!